The use of Self Contained Underwater Breathing Apparatus has increased free-diving operations greatly over recent years, permitting divers to enter the sea for a diversity of work and recreation activities. In this environment there are hazards not found in the terrestrial environment. These include dangers of sharks, poisonous stings, nitrogen narcosis, embolisms, entrapments, disorientation, entanglement in monofilament fishing lines, exhaustion, panic and drowning. Because of these hazards, virtually all agencies that instruct and certify divers teach that one must always be accompanied by a "buddy".
In underwater work and sport two divers together have great need to communicate with one another over the details of approach to said work or sport. The constant decision over navigation as well as the constant need to express individual observations require a communication system to greatly enrich the diving experience.
However, despite all attempts to create an affordable, functional, and convenient underwater talking mechanism, one has not been made or marketed. Without such a much-needed invention, divers are virtually mute. The loudest shout into present-day breathing apparatus only slightly enters the sound-conducting medium of the water and can rarely be heard by an adjacent diver. Communication is therefore reduced to hand signals. These are capable of only rudimentary expression and only when there is direct visual contact between the parties. Such directed attention precludes most other desired underwater activity, even when the water is clear. Often it is not clear, and this rudimentary mode of communication is then virtually impossible. For these reasons, since diver-to-diver communication is so difficult, the help that a buddy-diver could give in any instance of trouble, if expression of the danger or of predicament were more possible, is largely compromised. Consequently, divers ignore the hazards to some extent and dive, if with a "buddy", with little or no communication.
Many attempts have been made to provide divers with voice communication means. Indeed, the surrounding medium of sea- or fresh-water is an excellent conductor of sound. Sound energy, once in the water, is easily heard through the bones of the face and skull. But these attempts have failed to make a complete and simple solution for reasons to be recounted.
The teachings of Laughlin et al., U.S. Pat. No. 3,174,129, and of Martelli et al., U.S. Pat. No. 3,210,723, refer to electromagnetic mechanisms wherein the diver's voice is picked up in an enclosure around the mouth which contains a microphone which then causes an electromagnetic device to issue the sound into the water. Although such devices can be made to function with distance and sufficient clarity to provide inter-diver communication, they are subject to distortion of the sound, a nuisance, and to seawater leakage which in electrical circuits is a disaster. Whether for these reasons or because they are relatively expensive, combersome and inconvenient, such devices have not found a significant niche in the diver market to provide a solution to the problem of diver muteness.
The teachings of Hogan et al., U.S. Pat. No. 2,844,212, and of Alexander, U.S. Pat. No. 3,828,887, though professing a diaphragm means for the issue of sound into the surrounding water, are ineffective. This is because the diaphragm, having one face in contact with the water and the opposite in contact with the air, sits at the interface between two media of widely different acoustic impedances. Sound in air is almost completely reflected back into the air from these diaphragms without entering the water. Audible sounds passed are so faint as to require great acoustic silence for another diver to hear them, even at a distance of less than arm-length. Ordinarily, the sound environment of the marine diver is noisy due to sounds of molusks, fish, water movements and of the greatest noise generator, almost constantly present, the diver's exhalation bubbles. A major problem to the understandable perception of even quite loud underwater voice sounds in this noise of exhalation bubbles issuing from each diver's breathing regulator. That these bubbles normally pass the face, still generating some noise as they grow and coalesce, is a further disturbance to the sense of hearing of each individual diver.
The teachings of Minton et al., U.S. Pat. No. 3,123,680, Cupp et al., U.S. Pat. No. 3,347,230, and of Walters, U.S. Pat. No. 4,031,888, are merely mouth surrounds which permit lip movements of speech but which have no mechanical sound-emitting mechanisms in their makeup as in Hogan and Alexander. Although all are professedly to facilitate a microphone, Walters professes some "limited distance" effectiveness with his invention unassisted. That distance on all such devices, by this inventor's research, is so short as to be impractical, again due to lack of any means to match acoustical impedances.
This applicant's prior U.S. Pat. No. 4,071,110 provides a mouthpiece attached to the normal scuba regulator to accommodate normal breathing and with mechanical means to transfer a voice to the surrounding water through an acoustic impedance-match by means of a mechanical transformer, consisting of a diaphragm, lever system, and emitter.
The teachings of Williams, U.S. Pat. No. 4,183,422, reveal a balloon means which, if held to the mouth, involving both hands and the removal of the breathing regulator mouthpiece, can be inflated with some or most of the divers available breath and then, with the remaining held breath, spoken into to communicate to another diver. This devising has been know in some forms for many years. It does function, owing to the relatively large surface exposed to the impact of the voice in air, and to the multiple internal reflections without substantial reflection back into the speaker's mouth. These cause some penetration of the sound from air, through the rubber of the balloon, into the higher acoustical impedance of the water. Since no bubbles are allowed to escape, they generate no disturbance noise emanating from the speaker. The exhaust bubble noises of all listeners, nonetheless, provide masking unless they are aware of the attempted communication and suspend exhalation. While this balloon has a usable distance and clarity, though there are substantial losses, its great disadvantage is the requirement to suspend all other underwater activities, including breathing, to employ hands, mouth, and lungs in the unusual procedure which fully occupies them, preempting normal activities.
While the prior patent of this applicant provides acoustical impedance-matching means in a convenient packaging, its development has revealed a difficulty in finding sufficiently good sound-absorbent material which backs the diaphragm. The purpose of said material is to reduce nullification of sound-pressure across said diaphragm. No material has been found which can be wetted without alteration of its sound-absorbency nature. Without this its sound projection is lessened and the annoyance of bubble-noise makes communication tenuous. In addition, the diaphragm and lever mechanisms, while rugged and capable of wetting without damage, are of the nature of fine instruments, requiring some detailed adjustment and care in manufacture.
It is the purpose of this disclosure to reveal a much simpler means of acoustical impedance-matching conceived during testing of my prior invention, which means, when incorporated into the other features of an underwater communicator, eliminates need for diaphragms, levers and of emitter mechanisms, the whole being capable of simple injection molding. Also disclosed is a bubble silencer described and claimed in the previously mentioned copending application. The bubble silencer frees the diver of the proximal noise of his own bubbles and he can thus hear words of another using such a communicator.